The present invention is an improved packer for water wells which is especially used in sandy areas. The conventional packer now in use consists of a short metal pipe, usually steel, threaded on the inside at both ends. In use the conventional packer is threaded so that it can be attached to a well casing, then a screen is usually attached to the opposite end of the packer. A packer has to be designed to insure that the water or liquid below it in the well flows through the packer, not between the packer and the pipe casing or the adjacent strata of earth. Therefore, the packer has a means for stopping the flow of liquid around it. There are a great number of methods in the prior art used to achieve this goal. The one most used is to place one or more annular rings on the outside of the packer. These annular rings can be about any shape. P. Kollsman-Patent No. 3,305,367 1968 in FIGS. 1 through 12 shows many of the shapes these annular rings could take. No matter what the shape of the annular rings, they work by fitting tight against the wall of the casing. Basically, all of the methods of stopping the flow work on the principal of fitting tightly against the casing so that no water can pass. Some packers have packs that expand against the casing after they are placed in the well casing. The usual method of causing this expansion is compression on the packer or having a ring or part that expands when wet. Another expansion method is expansion of a balloon-like structure against the pipe casing with a gas. Most conventional packer also contains annular rings made out of elastomer material, usually rubber, around the outside to provide a seal between the packer and the adjacent strata of earth.
One problem with this packer is that it is made out of metal, usually steel. This usually leads to corrosion of the packer as well as corrosion of the well casing and screen, leading to a shorter life for the screen as well as the well casing. The metal packer conducts electricity which allows the electro chemical reaction to take place, causing corrosion. Also, there is the possibility of the two casings and the screen touching when they are screwed into the metal packer. This would cause corrosion of the well casing and screen.
Another problem with this packer is that it is made of two different materials: metal, usually steel, and an elastomer material, usually rubber. The metal portion is usually casted, then threaded, and then the rubber portion is molded on the outside. This two-step process makes the packer expensive to manufacture. Also, there are problems with the rubber metal bond that shortens the life of the packer. The use of rubber as the elastomer material also causes problems in that it is susceptible to tearing. The fact that the packer is made out of metal makes it rather heavy, and thus, makes it expensive to ship and awkward to work with.
There are numerous advantages of the invention. First, the packer is made out of plastic. The plastic chosen for the packer has outstanding hydrolysis resistance and will not corrode like metal. The invention also insures a longer life of the well casing and screen, since the plastic packer will not enhance corrosion of the well casing and the screen. The plastic will not allow the flow of electricity from the well casing to the screen. Secondly, the plastic packer has a protective annular ridge on its inside that keeps the well casing and screen from touching. These two features eliminate any corrosion or the enhancement of corrosion that could be caused by the packer.
Another advantage is that the plastic packer is made of one material. This means it can be molded in a single step process. Therefore, the plastic packer can be produced easier and with less expense. Also, since it is made out of one material, one does not have to worry about the metal to rubber bonds, and the problems with this bond. If the plastic packer is made out of polyurethane, it will have much better tear resistance than the rubber used on the conventional packer. This will make the annular ring seals much tougher and more resistant to tearing. Lastly, the plastic packer weighs substantially less than the conventional metal packer. This makes it less expensive to ship to the job site and less awkward to work with at the job site.
The object of this invention is to produce a packer that is easier and less expensive to manufacture, less expensive to ship, easier to work with, has a long life, and will not cause corrosion of other parts. The main features that make the invention achieve these objectives is that the packer is made of only one material, plastic, and that it has a protective annular ridge on the inside of the packer to insure that the well casing and the screen do not meet.